JPH03157839A - High frequency modulated magnetic field generating device for magneto-optical disk - Google Patents

Abstract

PURPOSE:To generate a high frequency modulated magnetic field with a low driving voltage and a low power consumption by switching the flow state and the non-flow state to a first coil by the current flowing to a second coil where the energy to invert the current flowing to the first coil is stored. CONSTITUTION:A first coil 7 which gives the modulated magnetic field for recording to a magneto-optical recording medium, second coils 4 and 5 where the energy to invert the current flowing to the first coil is stored, and switches 8 and 9 for switching between the flow state and the non-flow state of the current flowing in second coils 4 and 5 to the first coil 7 are provided. When the current equal to the current flowing to the first coil 7 is preliminarily supplied to second coils 4 and 5 to store the energy and second coils 4 and 5 and the fist coil 7 are connected in this state, the current flowing to the first coil 7 quickly rises by the constant current action of second coils 4 and 5 and becomes equal to the current flowing to second coils 4 and 5. Thus, the magnetic field generating coil which has a low supply voltage and a large inductance is modulated with a high frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high frequency modulated magnetic field generating device used in a magneto-optical recording device using an overridable magnetic field modulation method.

With the development of electronic computers, low-cost, high-capacity auxiliary storage devices (7) and magneto-optical disks are expected in many fields. (ζ Many override methods have been proposed. One of them is to fix the intensity of the laser beam.
There is a magnetic field modulation method that performs recording by modulating the direction of the bias magnetic field (Japanese Unexamined Patent Publication No. 48806).This method of modulating the bias magnetic field involves changing the direction of the magnetic field generating coil current using a switching element or the like. There is a method of inverting and modulating it.

An example of the above-mentioned conventional modulated magnetic field generator will be described below with reference to the drawings.

FIG. 5 shows a conventional modulated magnetic field generator.
1 is a voltage source that applies a constant voltage V8 to the magnetic field generating coil. 5 is a magnetic field generating coil, which is a magneto-optical recording medium (not shown)
A bias magnetic field for information recording is applied to the 4 is the DC resistance of the magnetic field generating coil. 2. 3. 6. 7 is a switch such as a transistor that changes the direction of the current flowing through the magnetic field generating coil, and 48.9 is a current source that limits the current flowing through the magnetic field generating coil to 8. 1o is 2
, 3°6.7.

The operation of the modulated magnetic field generator configured as described above will be explained below.By turning on switches 2 and 7 and turning off switches 3 and 6, direct current from the constant voltage source 1 to the switch 2° magnetic field generating coil is generated. Resistance 4. 1 through the magnetic field generating coil 5° switch 7 and constant current source 8. A current flows to apply a bias magnetic field to the magneto-optical recording medium, and switches 3 and 6 are turned on, and switch 2 is turned on.
By turning off and 7, a current flows in the magnetic field generating coil in the opposite direction to the above, and the bias magnetic field is reversed.By switching between these two states in accordance with the recorded data, this device generates a modulated magnetic field. (a) Problems to be Solved by the Invention However, the above configuration has the following problems. Figure 6 shows the changes in . t+, tal This is the time when switches 2 and 3°6.7 are switched to the state where the magnetic field generating coil current is reversed. The current of the magnetic field generating coil (R/ as shown in Table 6)
It changes with the time constant of L+, and a certain amount of time is required for the current to reverse. Due to this time constant, it is difficult to generate a high frequency modulated magnetic field with this device, but the following two methods can shorten the current reversal time in conventional devices.
There is one.

(1) Decrease the inductance of the magnetic field generating coil (2) Increase the direct current resistance of the magnetic field generating coil However, there is a limit to (1) in order to apply a sufficient magnetic field to the magneto-optical recording medium. In addition, (2) has the problem that the power supply voltage Vs required to flow a sufficient current through the magnetic field generating coil becomes high and the power consumption of the circuit increases. The present invention provides a device capable of modulating a magnetic field generating coil having a large inductance with a low power supply voltage at a high frequency.

Means for Solving the Problems In order to solve the above problems, the high frequency modulated magnetic field generator G of the present invention includes a first coil that applies a modulated magnetic field for recording to a magneto-optical recording medium, and a current flowing through the first coil. It has a second coil that stores energy for reversal, and is equipped with a means for switching between a state in which the current flowing in the second coil is flowing in the first coil and a state in which it is not flowing. .

Effect of the present invention With the above-described configuration, a current equivalent to the current flowing through the first coil is passed through the second coil in advance. This stores enough energy in the second coil to rapidly match the current in the first coil. When the second coil and the first coil are connected, the current flowing through the first coil rapidly rises and becomes equal to the current flowing through the second coil due to the constant current effect of the second coil. Also, if a current flows through the first coil before connection, L If the energy stored in the second coil is sufficiently larger than the initial energy that the first coil had, then the current flowing through the first coil due to connection is It quickly becomes equivalent to the current flowing through the second coil. This allows the current in the first coil to be rapidly reversed.

Embodiments and above In describing the embodiments of the present invention, the third
The concept of the present invention will be explained using the drawings and FIG.

In Figure 3, l is the voltage V that supplies voltage to the coil.
s constant voltage source 2 is 1. 4 is a coil with inductance L2 that stores the energy of current reversal (corresponding to the second coil), 6 is a magnetic field generating coil DC resistance (assumed to have a value of R), 7 is a magnetic field generating coil with inductance L1 8 is a switch for controlling the current. When the switch 8 is on, a current of -I@ (positive current in the 6->7 direction) is flowing through the magnetic field generating coil.When the switch 8 is off, the current from the current source 2 is flowing through the magnetic field generating coil 7. It starts to flow. , 'l, the time variation of the current flowing through the switch 8 is shown in FIG. The switch 8 is turned off at time t1 and completely turned off at time t2. a is the switching time of switch 8;

The current change I (t) of the magnetic field generating coil is 11≦[ku,[
2, I(1) is t≧t2 and I(t,)==I.

becomes.

If the accumulated energy of the coil 4 is inscribed into the accumulated energy of the magnetic field generating coil 7 and made sufficiently large, (L+(L
2) If t1≦t≦t2, is ■(t)=−i −+ t If t≧t2, I (t)= ).

Therefore, the current in the magnetic field generating coil can be rapidly reversed from 1 ll to ja in time a.Next, a high frequency modulated magnetic field generating device according to a specific embodiment of the present invention will be explained with reference to FIG. do.

In Figure 1, l is a constant current wire 2, 3 that provides voltage to the magnetic field generating coil, constant current wires 4, 5 are coils J that store the energy necessary to reverse the current of the magnetic field generating coil.
tz, 6 is a DC resistance of the magnetic field generating coil, 7 is a magnetic field generating coil, 8 and 9 are switching elements -P that control the direction of current in the magnetic field generating coils, and 10 is a control unit that controls the state of the switching elements. The operation of the high-frequency modulated magnetic field generator configured as above will be explained below.With 8 on and 9 off, l ->2->4-
>8 and ■• currents flow, and energy is accumulated in the coil 4. Also 1->3->5・->7->6->8
When the current is IA, the magnetic field generating coil 7 generates a magnetic field. From this state, when 9 is turned on and 8 is turned off, the current flowing through the coil 5 passes through 9 to ground, and the current flowing through the coil 4 changes to 6. 7. Even if the direction of the current in the magnetic field generating coil is reversed, the reversal time of this current (as mentioned above, it is equivalent to the switching time of switching element 8. From this state, 8 is turned on again. .

9 is turned off, the current flowing in the coil 5 flows into the magnetic field generating coil 7, and the current in the magnetic field generating coil is reversed at high speed.

Figure 2(a) shows the current waveform when a magnetic field generating coil with an inductance of lμH is driven by this device.At the same time, the current waveform when the same magnetic field generating coil is driven by a conventional device is shown. It is shown in FIG. 2(b).

In the conventional device, the DC resistance of the magnetic field generating coil is set to 50 Ω in order to speed up the current reversal time.In the device of the present invention, the current reversal time is 10 ns, and the
It is now possible to modulate the magnetic field at a frequency more than twice as high.In addition, while conventional devices required a power supply voltage of 20V, this device can reduce the power supply voltage to 5V. The effect of the invention was that the power output was reduced to 2.5W, thereby realizing miniaturization and low heat generation of the device.Like the above, the present invention has the following advantages: A second coil is provided to store energy for reversing the flowing current.By providing a means for switching between the state in which the current flowing in the second coil is flowing in the first coil and the state in which it is not flowing, it is possible to reduce the Driving Voltage It is possible to provide a device that consumes low power and can generate a high-frequency modulated magnetic field.

[Brief explanation of the drawing]

Figure 1 shows the configuration of the high-frequency modulated magnetic field generator according to the embodiment of the present invention. Figure 2 (a) shows the drive current waveform of the magnetic field generating coil in the embodiment of the present invention. Figure 2 (1)) shows the modulation of the conventional example. Figure 3 shows a conceptual diagram of the device in the Q-0- embodiment of the present invention; Figure 4 shows the switching characteristics of the switching element shown in Figure 3; Figure 5 shows the conventional modulated magnetic field. The configuration of the generator is as follows. Figure 6 is a diagram of the drive current waveform of the magnetic field generating coil by the conventional modulated magnetic field generator. Storage coil, 6...Magnetic field generation coil DC resistance 7...Magnetic field generation coil 7, 8. 9...Switching element, lO...Control gear

Claims (2)

[Claims] (1) A first coil that applies a modulated magnetic field for recording to a magneto-optical recording medium, and a second coil that stores energy for reversing the current flowing through the first coil, and the second coil A high frequency modulated magnetic field generating device comprising means for switching between a state in which a current is flowing through the first coil and a state in which a current is not flowing in the first coil. (2) The high frequency modulated magnetic field generating device according to claim 1, further comprising a plurality of coils that store energy for reversing the current flowing through the first coil.